<form class="form-horizontal" role="form">
  <div class="form-group">
    <label for="firstname" class="col-sm-2 control-label">用户名</label>
    <div class="col-sm-10">
      <input type="text" class="form-control" id="firstname" placeholder="用户名">
    </div>
  </div>
  <div class="form-group">
    <label for="lastname" class="col-sm-2 control-label">密码</label>
    <div class="col-sm-10">
      <input type="text" class="form-control" id="lastname" placeholder="用户密码">
    </div>
  </div>
  <div class="form-group">
    <div class="col-sm-offset-2 col-sm-10">
      <button type="submit" class="btn btn-default">登录</button>
    </div>
  </div>
</form>